Spirometry is the key test for COPD and asthma. A low FEV1/FVC ratio means air cannot be blown out quickly – obstruction. A normal ratio with a low FVC suggests restriction, which needs full lung function tests to confirm.
How to use the FEV1/FVC Ratio Calculator
- FEV1
- FVC
- FEV1 % predicted
- FVC % predicted
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter FEV1 and FVC from post-bronchodilator spirometry, and FEV1 % predicted if known.
Inputs explained
| Field | What to enter |
|---|---|
| FEV1 | In L |
| FVC | In L |
| FEV1 % predicted | In % |
| FVC % predicted | In % |
Example values
How the main result changes when FEV1 changes and everything else stays at the example values above:
| FEV1 (L) | FEV1/FVC ratio |
|---|---|
| 1.05 | 0.31 |
| 1.58 | 0.46 |
| 2.1 | 0.62 |
| 2.63 | 0.77 |
| 3.15 | 0.93 |
| 4.2 | 1.24 |
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
FEV1/FVC = FEV1 ÷ FVC
Obstruction: post-bronchodilator FEV1/FVC < 0.70 (or below the lower limit of normal)
GOLD: ≥ 80% predicted 1 (mild) · 50–79% 2 (moderate) · 30–49% 3 (severe) · < 30% 4 (very severe)
Worked example
Inputs — FEV1: 2.1 L; FVC: 3.4 L; FEV1 % predicted: 62 %; FVC % predicted: 85 %.
Results — FEV1/FVC ratio = 0.62; Pattern = Obstructive; GOLD grade (if obstruction) = GOLD 2 – moderate.
Key terms
- FEV1
- Forced expiratory volume in 1 second.
- FVC
- Forced vital capacity.
Frequently asked questions
What is a normal FEV1/FVC ratio?
Above 0.70 in adults; it falls slightly with age, so some guidelines use the lower limit of normal.
What does a low FEV1/FVC mean?
Airflow obstruction, as in COPD or asthma.
Why test after a bronchodilator?
COPD is defined by obstruction that persists after a bronchodilator.